"There's definitely an unconscious bias and dare I say it - discrimination - when it comes to closing the pay gap.

"I mean, we continue to feature in the lower end of the spectrum - the lowest, even."

The data is based on average wages recorded in Statistics NZ's Labour Market Statistics. Using this data, the overall gender pay gap is 86 percent, with women's average wage at $27 an hour, compared to men's at $31.

That's a larger gap than the 9.2 percent pay gap calculated by Statistics NZ. That's because Stats NZ's preferred methodology uses median pay, which it says is more representative. The CTU uses the mean, saying taking account of the extremes is more accurate, especially as men are more likely to be in the highest-paying jobs.

The CTU says the pay gap isn't just about gender.

"It's about discrimination, and the impact compounds on people who are already discriminated against by factors like racism.

"Over a working lifetime, this adds up to opportunities for health, security and freedom that New Zealand women and their whole families are missing out on by lottery of birth," Council of Trade Unions President Richard Wagstaff said.

"It's the Pacific women who keep the fires burning - doing jobs the rest of the country won't do, but are still equally important."

He said the Government's pay equity legislation and increasing the minimum wage will help reduce the gap, but said the community also need to address it.

"I think the women's movement itself must focus on women who are the bottom of the equity scale.

"From my perspective, men have just got to get on board. I am referring to powerful men who are in situations of influence - those who own companies paying women workers of the night economy. They need to get on board and do all they can to reduce pay inequities."

National's spokesperson for women Paula Bennett says "the gender pay gap is still too high and it will remain too high until it no longer exists.

"The National-led Government introduced pay equity principles and settled a $2 billion pay equity claim for 55,000 care and support workers. We will continue to fight for pay equity and equality."